After 18 years of legal entanglements, the Federal Communications Commission has granted United Broadcasting Co. Inc. a license renewal for WDJY-FM (100.3).

The 3-to-1 vote reverses a review board decision of 1983 to grant the station's license to District Broadcasting Co. The action also denies the application from another local company and overturns another decision against United by an administrative law judge.

The complicated case dates back to 1966 when United was last granted a license for the station, which was known as WOOK until earlier this year. Subsequently, the license was deferred by the FCC while the commission examined the internal workings of two other United properties and ultimately revoked their licenses. In addition, competing applications for WOOK set off six more years of hearings and appeals.

Earlier this week officials of United, a Bethesda-based corporation with nine radio stations and two cable companies, said they expected the two other companies to appeal last week's FCC decision.

Jerry Hroblak, chairman and president of United, said in a statement this week: "All broadcasters should be assured that a dedication to community service and an uncompromising observance of commission rules will be recognized in the comparative hearing process."

In 1975 United lost WFAB-AM in Miami and WOOK-AM in Washington after the FCC found the station had broadcast misleading advertising and lottery information and fined United $6,000 for rule violations on its AM properties.

United has continued to operate WDJY while it appealed the decisions against the company.

In its decision last week, the FCC noted that the review board should have considered the remedial steps taken by United after its problems with the AM stations. The commission found "those measures substantial and persuasive of United's ability to prevent further serious misconduct at WOOK-FM. . ." Dial Shifts

Starting Jan. 21 political commentator Mark Shields will switch his analysis base to WMAL-AM (630). His reports had been fed to WTOP-AM (1500) by Mutual Broadcasting but the election-keyed reports were slated to end this week. Shields will be on WMAL for five minutes daily at 6:30 p.m. . . . Casey Carson, the morning man at WDJY, left the station last week for another job, according to the station, and a replacement is expected to be named next week. WAVA-FM (105.1) is expected to name its new morning voice in a few days . . . Jim Scott, the popular marine-news editor at WNAV-AM (1430) in Annapolis, has signed off after 11 years and nearly 4,000 broadcasts. Cabbage Patch Auction

WPGC-FM (95.5) is auctioning off a supply of 20 Cabbage Patch dolls, starting at 6:45 a.m. today and continuing through the weekend. The highest bidder has to make a check out to a favorite charity before collecting the doll. Holiday Happenings

WMAL and WRQX-FM (107.3) are cosponsors with Mayor Marion Barry's Committee to Promote Washington of the free bash along Pennsylvania Avenue outside the Old Post Office on New Year's Eve. The action starts around 8 p.m. and both stations will broadcast some of the highlights of the Four Tops, the Slickee Boys, Roy Ayers, the Mike Crotty Orchestra, Stacy Lattisaw and Sylvia Traymore . . . Then, a mile or so away at 9 p.m., WRC-AM (980) is bringing its band downtown for an old-fashioned ball at the Vista International Hotel. The Kidney Foundation will be the beneficiary of this joint project with Raleigh's . . . WAVA is hosting a free party at Rumors, 19th and M streets, at 9 p.m. . . . WPGC will be joining the 7-Eleven stores to give free coffee to those on the road from 7 p.m. to 7 a.m. Other Year-End Mixers

10 a.m.: WRQX will present "News That Rocked '84," a look back at Marvin Gaye, Prince, Julian Lennon, Culture Club, the Jacksons, Hall & Oates and more until noon.

2 p.m.: WDJY will start a 10-hour countdown, which will include interviews with Dennis Edward, Billy Ocean, Joyce Kennedy and others.

6 p.m.: WWDC-FM (101.1) will play the top 101 records of 1984. At 9 p.m. DC-101 will broadcast an already sold-out party from the Hyatt Arlington featuring its zany disc jockeys.

7 p.m.: WXTR-FM (104.1) will feature a Wolfman Jack special with classic rock 'n' roll, including Wolfman's own unique countdown at midnight.

8 p.m.: WWDC-AM (1260). Eddie Gallaher starts spinning the best of the big-band era.

8 p.m.: WAMU-FM (88.5). Rob Bamberger kicks off hot jazz and dance bands from the 1920s through the 1940s, along with some original broadcasts by Benny Goodman and Artie Shaw. Listeners can phone in their requests on 885-8850.

8 p.m.: WETA-FM (90.9) will broadcast the New York Philharmonic's gala from Lincoln Center at 8 p.m. Simulcast on WETA TV (Channel 26).

10:55 p.m.: WMZQ-FM (98.7) will feature Willie Nelson's bash live from Houston for 2 1/2 hours. The Nelson affair with Waylon Jennings, B.B. King and others will be simulcast on Home Box Office.

11 p.m.: WGMS-FM (103.5) will feature Paul Anthony playing the best of the big bands.